Memory devices are typically provided as internal, semiconductor, integrated circuits in computers or other electronic devices. There are many different types of memory, including random-access memory (RAM), read only memory (ROM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), flash memory, and resistance variable memory, among others.
Types of resistance variable memory include programmable conductor memory, phase change random access memory (PCRAM), and resistive random access memory (RRAM), among others. A physical layout of a PCRAM memory device may resemble that of a DRAM device, with the capacitor of the DRAM cell being replaced by a phase change material, such as Germanium-Antimony-Telluride (GST). A physical layout of an RRAM memory device may include memory cells including a variable resistor thin film, e.g., a colossal magnetoresistive material, which may be connected to an access device, such as a diode, a field effect transistor (FET), or a bipolar junction transistor (BJT), for example.
The memory cell material of a PCRAM device, e.g., GST, may exist in an amorphous, higher resistance state, or a crystalline, lower resistance state. The resistance state of the PCRAM cell may be altered by applying sources of energy to the cell, such as current pulses or pulses of light, among other sources of energy. For example, the resistance state of the PCRAM cell may be altered by heating the cell with a programming current. This results in the PCRAM cell being programmed to a particular resistance state, which may correspond to a data state. In a binary system, for example, the amorphous, higher resistance state may correspond to a data state of 1, and the crystalline, lower resistance state may correspond to a data state of 0. However, the choice of these corresponding data states may be reversed, that is, in other binary systems, the amorphous, higher resistance state may correspond to a data state of 0, and the crystalline, lower resistance state may correspond to a data state of 1. The resistance state of an RRAM cell, e.g., the variable resistor thin film, may be increased and/or decreased by applying positive and/or negative electrical pulses across the film. This may result in the RRAM cell being programmed to a particular resistance state.
Methods for processing, e.g., fabricating, memory, such as resistance variable memory, may include chemical vapor deposition (CVD) and atomic layer deposition (ALD), among others. CVD may include mixing a number of reactants in a chamber to form a material, e.g., a resistance variable material, which subsequently deposits across exposed surfaces of a number of semiconductor structures and/or substrates. ALD may include forming thin films of material by repeatedly depositing monoatomic layers in a chamber. For example, ALD may include individually depositing a number of reactants, e.g., precursors, that react in situ to form a desired film of material, e.g., resistance variable material, across a number of semiconductor structures and/or substrates.
More specifically, ALD may include introducing a first reactant in a chamber, which reacts with a number of structures and/or substrates to form a self limiting layer across the structures and/or substrates. After the layer is formed, the excess first reactant may be evacuated from the chamber, and a second reactant may be subsequently introduced in the chamber. The second reactant may react with the layer to convert the layer into a desired material, e.g., resistance variable material, layer over the structures and/or substrates.